Rotary hook sewing machine



March 9,' 1937.

N. v. cHIsTENsEN 2,073,593 ROTARY noox SEWINGVHAGHINE Fired Nov; 24, 19:54 :s sheets-sheet i Mardi 9, 1937. N.`v. cHmsTENsEN f I 250735593 l ROTARY' Hoon SEWING MAcHINE A I Filed No'v. 24, 19:54 :s snegtsfsheet 2 zal \i ,zal

Mag-ch 9, 1937. N. v. cHRls'rl-:NSEN

n ROTARY Hooi: SEWING monum- Filed Nov. '24, 1934 s sheets-sheet s Emmi I N V TOR.- Norm/m VCH rroRNEYs Patented Mar. 9, 1937 UNITED STATES ROTARY HOOK SEWING MACHINE.

Norman V. Christensen, Chicago, Ill., assignor to Union Special Machine' Company, Chicago, Ill., a corporation of Illinois Application November 24, 1934, serial Nn. 754,566

7 Claims.

This invention relates to rotary hook sewing machines, and it has reference more particularly to means for cooling the rotary hooks and keeping them free of lint and dirt.

I Incident to high speedoperation of machines of the kind referred to, considerable heat is generated by the rapid rotation-ofthe rotary hook, as a consequence -of which it m'ust be discarded and replaced after a comparatively short period 10 of service. 'I'his condition is aggravated by blanketing of the hook surfaces with lint which operates as insulation preventing ready dissipation from the hook of the heat generated by its rapid motion.

The purpose of my invention is to obviate this difculty and lengthen the term .of service of the rotary hook. This I accomplish by provision of reciprocating pump means capable' of producing a substantiallyV continuous blast o f cooling air,

and of means for discharging this air blast upon the rotary hook in such manner as to effectively cool thel same and to prevent lint and dirt from collecting upon it, so that heat dissipation may take place freely by radiation and by convection.

In the drawings, Fig. I is a fragmentary view partly in plan and partly in section showing a rotary hook sewing machine embodying my invention.

Fig. II is a staggered longitudinal section taken as indicated by the arrows II-II in Fig. I.

Fig. III is a cross section taken as indicated by the arrows III--lII in Fig.- I.

Fig. IV'is a longitudinal section through the piston of the pump means which produces the cooling air blast.

Fig. V is an end elevation of the piston as viewed from the right in Fig. IV.

Fig. VI is a sectional view of the pump 'taken as indicated by the arrows VI VI in Fig. 'II and 40 drawn to a larger scale; and

Fig. VII is a view similar to Fig. I showing an alternative embodiment of my invention.

' With more detailed reference rst to Figs. I-VI of these illustrations, I designates the worksupporting plate of the sewing machine. Be-

neath this are the bearings wherein -the main shaft 2 of the machine is journaled. The stitch forming mechanismof the machine includes a rotary hook 3 surrounding a non-rotating bobbin holder 4, and a bobbin case 5 holding a bobbln.`

There is necessarily frictional engagement of the hook with the holder. ,The hook member 3 is secured to the protruding end of a countershaft 6 journaled in the boss 'I of the housing 8, through whicnthe main shaft 2 extends. Mount- A suction-responsive,

ed on the main shaft 2 within the housing 8 is a spur gear wheel 9 which drives an intermeshing gear I0 on the countershaft 6, the gear ratio being such that the countershaft is caused to rctate twice for each rotation of the main shaft E, and therefore twice for each stitch. Attached tothe underside of the work-supporting plate I, by means of screws II, is a pump cylinder I2 within which reciprocates a hollow piston I3 (Figs. III, IV and VI) formed at one end with a flat-sided, integral, axial projection I4. The piston I3 is actuated by an eccentric I5 on the main shaft 2, whereof the strap I6 has a clevised extremity Il (Fig. I) which engages over the axial projection I4 of said piston and whereto it is pivotally connected by a pin I8. The piston I3 is lubricated by oil or grease introduced through a hole I9 (Fig. III) in the work-plate I of the machine, and said piston is provided with a circumferential groove ,20 to facilitate flow ol the lubricant thereabout. At its outer end the piston is provided with openings I3a so that air may freely circulate through it to keep it cool.

During the suction strokes of the piston I3, air is drawn into the cylinder I2 through a lateral inlet .port 2I in the closed or head end I2 of said cylinder under the control of a spring-influenced, ball `checl: valve 23. As shown in Fig. VI, this check valve 23 is disposed in a cylindric hollow 24 which is coaxial with the inlet port 2l, and which communicates with the interior of the cylinder I2 by way o'f a connecting port 25. During the pressure strokes of the piston I3, air drawn in as above explained, is compressed and forced pasta spring-influenced, pressure-responsive, ball check valve 26 into'a tubular discharge nozzle 21, said valve 26 being disposedwithin the central enlargement 28 of an outlet port 29 which leads axially, from the chamber 24 into the nozzle.

Referring still to Fig. VI, ythe discharge nozzle .21 is connected to the cylinder I2 by a screw and clamp nut coupling 30 whereof the component 3I has an axial bore Vwhich constitutes the air outlet 29 from said cylinder. Referring to Figs. I and II it will be observedthat the end of the nozzle 21 is flattened and bent as at 3I so that the air is discharged upon the rotary hook 3 at a proper angle and from the rear, in the form of a definitely-directed, divergent stream or blast. In this way the air is caused to pass around the rotary hook 3 and also into the open back face of the same, thereby effectively cooling the parts, and, by virtue of impinging in part upon the `external surfaces and in part upon the internal surfaces, preventsl lint from collecting with avoidance of such blanketing as would be likely to interfere with the ready dissipation -of heat generated in the 5 hook by the frictional contact of the rapidly rotating hook member 3 with the bobbin case 5. The air stream delivered from the nozzle is substantially continuous in view of the rapidity of the pump reciprocations, and therefore effective under all conditions ofoperation. l

' In another form of my invention shown in Fig. VII, the flattened end 3Ia of the air dis-v charge nozzle 21a, is bent at right angles so that the air is discharged directly toward the periphery of the rotary hook By virtue of the divergency or spread of the air blast, parts of thestream will pass along the front and rear faces of the hook, so that the cooling and cleaning effect obtained is substantially the same as before. In

all other respects, the modification of Fig. VII is like the first embodiment of my invention. Accordingly, to obviate the necessity for repeti-v tive description, the lcorresponding parts have all been identified by the same reference numerals previously employed, with addition however,

in each instance, of the letter a for the purposes of distinction.

The nozzle, it will be understood, may be placed in various different positions, the effort in all cases being to so place it as to enable it to best perform its required function of simultaneously cooling and cleaning the rotary hook and the adjacent parts.

Through my invention it is possible to operate sewing machines at very much higher speeds than heretofore without attendant injurious effects upon the rotary hooks through overheating, notwithstanding the added load of the pump which I purposely actuate from the low speed shaft 2 so as to have a minimum retarding effect upon the machine mechanism.

Having thus described my invention, I claim:

1. In a sewing machine, the combination of a work supporting bed, a rotary hook disposed beneath said bed, an air discharge pipe adjacent and spaced from said hook and dimensioned so as to direct a stream of air on to said hook to completely envelop said hook for preventing the accumulation of lint on the hook and for cooling said hook.

2. In a sewing machine, the combination of a work supporting bed, an open rotary hook disposed beneath said bed and rotating on a bobbin holder, an air discharge pipe adjacent and spaced from said hook and dimensioned so as to direct a stream of air onto and through said hook to completely envelop it, for preventing the accumulation of lint thereon, and for cooling the interengaging surfaces of said hook and the bobbin casing. f i

3. In a sewing machine, the combination of an actuating shaft, a rotating hook operated from said actuating shaft, an air discharge pipe associated with said rotating hook, said'pipe being located at one side of the rotating hook and disposed so as to direct a stream of air onto and across said hook for preventing the accumulation of lint thereon and for cooling the same, means operated by said actuating shaft for supplying-air to said pipe, said last named means including a cylinder having a ported connection to said pipe, a check valve in said ported connection for preventing lair from being drawn from said pipe, a piston in said cylinder, and a check valve-controlled passage connecting said cylinder with the atmosphere.

4. In a sewing machine, the combination of an actuating shaft, a rotating hook operated from said actuating shaft and rotated twice for each rotation of the actuating shaft, anair discharge pipe associated with said rotating hook said pipe being located at one side of the rotating hook and disposed so as to direct a stream of air onto and across said hook for preventing the accumulation of lint thereon and for cooling the same, means for intermittently supplying said pipe with air,

and a check valve located between said air sup-5 plying means and the pipe for preventing air from being drawn from the pipe by the supplying means.

5. In a sewing machine. the combination of an actuating shaft, a rotatinghook operated from said actuating shaft and rotated twice for each rotation of the actuating shaft, an air discharge pipe associated with said rotating hook, said pipe being located at one side of the rotating hook and disposed so as to direct a stream of air onto and across said hook for preventing the accumulation of lint thereon and for cooling the same, a pump cylinder having a connection to said pipe, a check valve in said connection preventing air from being withdrawn from the pipe, and a piston operated by said main actuating shaft, said cylinder having a valve controlled port leading to the atmosphere whereby air is drawn from the atmosphere on the outward movement of the piston and delivered by the piston on the inward movement thereof to said pipe.

6. In a sewing machine, the combination of an actuating shaft, a rotating hook operated from said actuating shaft, an air discharge pipe located at one side' of .the actuating shaft and having the discharge end thereof spaced away from said rotating hook and disposed so as to direct a stream of air onto and across the peripheral portion of said rotating hook and at one side of the stitching point for preventing the accumulation of lint on said rotating hook and for cooling the same, and means for supplying air to said pipe.

7. In a sewing machine, the combination of an actuating shaft, a rotating hook operated from said actuating shaft, an air discharge pipe located at one side of said actuating shaft and disposed at one side of said rotating hook for directing a.

substantially constant stream of air onto and across .said lrotating hook for preventing the accumulation of lint thereon and for cooling the same, and means operated by said shaft for supplying air intermittently to said pipe for producing said air stream. a

NORMAN V. CHRISTENSEN. 

